In recent years, next-generation communication methods such as the long-term evolution (LTE) have been considered to be used for cellular phones, in addition to conventional methods such as the wideband-code division multiple access (W-CDMA) and the global system for mobile communications (GSM). The next-generation communication methods such as LTE are global standard specifications. Given this situation, a frequency configuration in wireless communications is being reviewed in various countries.
Cellular phone operators that provide cellular phone communications service use an increasing number of frequency bands (hereinafter, may be called bands) to accommodate the communications methods. Because this increases the number of bands that cellular phones need to deal with, a wireless block in cellular phones is designed with a markedly increasing number of wireless parts.
A few years ago, cellular phones only needed to have one band, but recent cellular phones deal with many bands such as Band I/V/IX, GSM850/900, and the digital cellular system (DCS)/the personal communications service (PCS). For example, the band of Band V is 824 to 849 MHz. The band of GSM850/900 is 824 to 915 MHz. For example, the band of Band I is 1920 to 1980 MHz. For example, the band of Band IX is 1750 to 1785 MHz. For example, the band of DCS/PCS is 1710 to 1910 MHz. Band V and GSM850/900, which have relatively low bands, are called LowBand. Band I, Band IX, and DCS/PCS, which have relatively high bands, are called HighBand.
In order to suppress the increase in the number of wireless parts caused by such an increase in the bands used, techniques for packaging GSM and for packaging two or more bands in W-CDMA in a transmitting amplifier have been developed. A multi-band/multi-mode power amplifier (PA) technique for amplifying both the communication methods of W-CDMA and GSM has also been developed.
Generally in the multi-band configuration, signals are collectively handled for bands in LowBand (824 to 915 MHz) and for bands in HighBand (1750 to 1980 MHz). In this case, two amplifiers are used for amplifying signals at the LowBand side and for amplifying signals at the HighBand side. To distribute output from the amplifiers to each band, a “2 in 5 out” configuration has been designed to include switches at the output sides of the amplifiers.
In such a multi-band configuration, a conventional technique has been developed in which output matching to a desired frequency is performed with a switch to switch among the outputs of the two transmitting amplifiers and the ground. Another conventional technique has been developed in which input-stage matching circuits are integrated.    Patent Literature 1: Japanese Patent Application Laid-open No. 2004-180135    Patent Literature 2: Japanese Patent Application Laid-open No. 10-190379